√[(2 1/2 )² -2× 2 1/2 × 1 1/3+ (1 1/3 )²]=
=√[(5/2 )² -2× 5/2 × 4/3+ (4/3 )²]=
=√(25/4-20/3+16/9)=
=√(25*9-20*12+16*4)/36=
=√(25*9-20*12+16*4)/36=
=√49/36=7/6
cu formula a²-2ab+b²=(a-b)²
√[(2 1/2 )² -2× 2 1/2 × 1 1/3+ (1 1/3 )²]=
=√(5/2 -4/3 )²=
=5/2-4/3=
=(15-8)/6=7/6